Space discharge device and circuits



Oct. 26, 1943. A. M. SKELLETT 2,332,977

I I SPACE DISCHARGE DEVICE AND CIRCUITS Filed July 31, 1941 I 4 Sheets-Sheet 1- FIG. 4 H65 j; IIIEE 7 2r 7 l7 can.

COIL

INVENTOR AM. SKELLETT ATTORNEY A. M. SKELLETT SPACE DISCHARGE DEVICE AND CIRCUITS Oct. 26, 1943;

Filed July 33, 1941 4 Sheets-Sheet 2 FIG. 6

OUTPUT FIG. 7

FOEgi/NG A M CONTROL AMP W. Mm ...A

400 f SUPPLY VOLTAGE aol POTENTIAL or PLATE! l a bi INVENTOR AM. SKELLETT ATTORNEY ANOM CUHRENT MILLIAMPERES Oct. 26, 1943. M. SKELLETT 2,332,977 SPACE DISCHARGE DEVICE AND CIRCUITS Filed July 31, 1941 4 Sheets-Sheet 3 FIG. /3

H6. /4 FIG/5 E 7 a g o 5 g 4 3 4 a a 40 -20 vars 2 1.50 470 I90 2/0 1230 was ON GRID yon-W144 i A m 8 FIG. /6 E t I I a t l s E E Q Q x l l l J D I I l l 40 3o 32 2a 24 20 I6 12 a 4 -o GRID MR5 POTENTIAL (MEGA rlvs) NI/ENTOR AM. SKELLETT ATTORNEY Oct. 26, 1943. .v g LETT 2,332,977

SPACE DISCHARGE DEVICE AND CIRCUITS Filed July 31, 1941 4 Sheets-Sheet 4 g aurpur /NVENTOR AM. SKELLETT A TTORNEV Patented Oct. 26,- 1943 e Albert M. Skellett, Madisom N."

assignor to Bell Telephone Laboratories, Incorporated, New York,'N. Y.,a corporation of New York r I Application July 31, 1941. Serial No. 4 4,2515

(chasm-27) l e 17 Claims. The present invention relates to space dis-- charge apparatus and circuits therefor. More particularly, the invention relates to a beam tube with provision for variably controlling the beam to secure novel and useful effects.

A general object of the invention is to augment the effect of a voltage variation b-yreaction :upon the beam control.

This may be attained in accordance with "the invention by self-focusing together with a suitable construction and arrangement of thetube electrodes. In the embodiments to be disclosed in detail hereinafter the emission from thecath -Q ode may go in part to a plate of comparatively large superficial area and in part to an anode o fsmallerarea when there is little or no coricentration of the emission into a beam. The output. current divides between the plate and anode under this condition and initially the emission is small and may be mainly to the plate. As the emission becomes concentrated into a beam,it goes in greater and greater proportionto the anode as the focusing increases.

"This increases the portion of the output current carried by the anode relative to that carried by the plate. The resultant decrease in plate "current causes a decrease in potential drop across its coupling resistor and hence, an increase in plate potential. This increase in plate potential greatly augments the space current in the tube by drawing out more electrons from the cathode.

The focusing is produced in part by reaction of the output current or voltage upon thebeamforming means so that an initial variation in a direction to increase the output current causes the v current to be further augmented by reaction, giving atrigger type operation somewhat similar to that obtained with a gas-filled tube;

The nature of the invention and its various objects and features will be more fully apparent from the following'detailed description of illustrative embodiments shown on the drawings.

'In the drawings, r

Fig. 1 is a perspective view partly broken away to show internal structure, of a tube construe tion in accordance with the present invention, pl y g magnetic focusing;

Fig. 2 is a plan view looking down from above in Fig lwith the tube itself. sectioned;

Fig. 2A is a similar partial view representing a modified magnetic yoke structure to provide relay operation; I r i i Figs. 3, 4, 5, 6, 7 and 8 are simplified schematic diagrams of circuits for using the tube of the ,invention with magnetic focusing;

Surrounding the Figs. 9, 10 and 11 sh w operatin 'characteristics for certain of the circuits of thetprevious fi r .7 it

Figs. 12, 18 and? 20 are diagrammatic plan views of electrostatically focused tubes. according to the invention; t I, I

Figs. .13, 17 and 19are circuit views using electrostatic focusing; and r i Figs. l4, l5 and 16 show operatingl characteristics for circuits using .electrostaticfocusing. Referring to Figs land 2,'the tube 'is shown as having a generally cylindricalshaped envelope l within which are, a'cathode 2; at the center, adapted to be heated by; a heater winding not shown but assumed to beinside the cathode in accordance with known practice; a grid 3 surrounding the cathode. a split cylinder or plate 4 in two sections with gaps diametrically opposite each other, and anodes 5, 5 positioned back ofthesegapsfl he '1' tube is a magnetic yoke 6 provided with a winding l, for producing a focusing field of the type more fully disclosed in my prior Patent 2,217,774, granted October 15,

1940. When the field is absent the emission from r the cathode spreads out in all directions going mostly to the plate 4 which has large superficial area; only a small portion reaching the relatively s'mallanodes 5. When the focusing-"field is at maximum strength the-emission is focused into two beamsshown at ll) in Fig. 2. converging on the anodes 5," so that practically the entire cathode emission'is directed toward the anodes.

No attempt is madein Fig. l to showfconstructional details but the 1 general construction is indicated. The electrodes are"supported'from a press H "by stiff 'rods l2, and a centering disc 8 of Micarta is shown abovethe tops of the electrodes with stubs l0 welded to the plates .and anodes and projecting through holes to'support the electrodes laterally. Cathode Zis shown with a stem also projecting through disc 8; as

do also the end of the grid supporting wires. 'The leads are brought outithrough' the' press, 45 1 the heater leads being shown at l 3 and the other leads, being numbered. the same as the corresponding electrodes. ITheTtwo "anodes. may be, connected together. within the tube and the two 3 plates may be connected together Withinmthe tube.

In the circuit ofyFig. afabattery is is contreated between the cathode 2, and in common; to

the anode 5 and plate 4, thejlatter being-positive.

A high resistance 16 is connected in thele ad to the plated. Focusing coil 1 is inserieswith both on the diameter oi tube us efi being 130 'v'o'lts'in one casejande flvolts in} the case of a "larger ture is retracted .tension'...

the anode and plate. Anindicator is connected in circuit at [9. Battery I1 and potentiometer resistance I8 enable potentials of difierent magnitudes to be applied to the grid as the slider is moved along the resistance.

Starting with the'grid bias beyond cut-011 and therefore with the space current zero, as the grid potential is made, less negative, electrons will start tojilow'to'the plate and anode, most of them going to the plate at first since there is little or no focusing. As thespace current is increased the focusing action increases due to curgiven in Fig. 10. The grid bias for this curve was +1 volt. As the plate voltage e is exceeded the'tube suddenly triggers on, and it triggers oil with decreasing plate voltage at f.

This action; as one example, may be applied to a relaxation oscillator, illustrated in Fig. 6, in

which the grid may be used but need not be used. The second external resistance 32 and large capacity $3 have been 'adeled to the basic circuit. Assuming the instant in the cycle at which the current through the tube is zero or at its minimum value, capacity 33 charges in serent in winding 1 and electrons are diverted from the plate to the anode. I NTZh'en a critical.

value of grid bias is reached [enough electrons are flowing to start appreciable focusing and as this degree of focusing takes placeit deprives the plate of electrons to a marked extent, diverting them to the anode. This causesthe potential of the plate to swing in the positive dir efie d e al h'e w re P t n ia d o across resistance I8, and this has the efiect of drawing out more electrons; thereby accelerating the; focusing 'actionand the tube triggerson.

" If now the grid bias istnade negativein increasing amount the tubewill for a time remain triggered on until, notwithstanding the high potential on the plate, the grid bias. is sufi'iicient :tojredu'ce. thespace eurrent below that necessary for focusing and the tube triggers. off.

s The 'entir'e'icycle, o'tjoperationis shown by the "plots on Fig. gthejc'ycle in this case. beginning with the plate fcurre'nt at a and the anode current at b and, progressing with the arrows.

around the. cycle finally returning to points and 11. In this case the tube triggers on at the tglridvoltage 'v'alue' b'and triggers'ofi at the'g'rid voltage va ue d. In this'case resistance" ifitwas 10 rnegohms and the plate voltage cle'pende'd"updiametertube icylindrical'plate, '3 inch diameter).,

circuit as at 25 in;v Fig. 2A and mounting j a movablearmature 26; opposite this gap, the structure I 6, 1may'itseli servejwith armature 26as a re- ,lay for closing contacts as shown. The arma- If the tubefis used as animpulse produceiz'. as

. in Fig.5; one output may-be provided at 21 for the .positive? pulses on phase with the driving voltage .at 2 l) and another-'outputat'iii' for the negative f pulses "(opposite phase) *i The positive pulses 'are eproduced'in the platleadin coupling resistor .29 which maybe apart of'resistor l6. Thene'g'a- .tive pulses are developed; in the anode lead in coupling resistor 30.

A trigger type action" may: be? obtained from a varying "the potential 1 supplied from" battery 15 (Fig. 3.) a'iidf adjusting the" grid" circuit at! 29 so to normal position by-springs rice with resistor s2; and as the potential builds up across condenser 33 the point e (Fig. 10) is reached at w hichthe tube triggers on and the condenser discharges through the tube thus loweringthe applied potential below the point (Fig. l0) and causing the tube to trigger off, after which the cycle repeats itself.

The grid may be used advantageously to syn- 'chronize 'the relaxation;nsciilations'with applied pulsesyar 'd a "circuit for this purposefisshownin Fig l The control p ulsei s applied through any suitable input COllp1ll1g,l11ll$tr9 td as, transformer 3e. The action of the tub'eis the same as n Fig. 6 exce t that the oscillationfs cannot occur unless the grid potential is driven in apositive direction, which is done by the contrm pulse. The oscillations may betaken on and fused "in'an output circuit coupled across resistor 3' 2 through capacity 36, for example. i a

I tfis found th'atover a certain range of su ply voltage a negative resistance eiiect is ch- I constant.

tamed-1n the circuit to the plateas .indicated by the characteristic givenin 'Fig. 'lljthe falling characteristic being between plate voltage values g and h, the current being current to the plate (cylinder) the anode 'potentialfbeingheld This arrest. may be made use or in various ways, one eX'ainplabe-ing given in Fig. "8 in which oscillations are "generated in the timed circuit sa sy-vine fas-a useful load such as an 9151194.? fi i' i i std at a s an z j I'hecha'racteiis'ticcurve forthis condition is antenna. The focusing coil 7 i's'inthis case connected between the cathode eamen-y l5. The plate (cylinder) is connected'to the resonant;

circuit I39 and to 'apoint'inbattery [5 of such vpoti'e'ntial'.as to cause operation' in-the region of :supply voltage in p which the falling {characteris- .tic occurs.- Over the negative resistance region,

increasing the semis-s1 of theplate (cylinder) inn-ea es the 'space icurrent, hence the focusing, with the result that the electrons are focused onto'th'e' lar' ode andthe current to the plate'decreases. A voltage swing between the terminals of resonant circuit 39 in the' direction corres zionding to increase in plate current causes a still further increase in 'plate current and inthe original voltage variation until the-condenser in .the tuned circuit becomes; charged in that direction whereupon'a reversalin'the process takes place'until the condenser is-charged to opposite potential, and the cycle repeats itself.

-; Generally similar results )to those described in connection with magnetie iocusingcan-also be obtained'by useof electrostatic focusing; A tube for such purpose is shown indiagram-inFig. 12, plan View. The elements"! 2,:-4.=and-f 5 are} the same as in the previous figures. "A'pa-ir of grid wires 4 I 42 5 one, onxeach sidei' oi" the cathode' and parallel rto'rthe' cathode'will focus thebeam when supplied with proper potential. In argue thispo- "tential is supplied from battery. M and' potenti- "ome'ter' resistanceiltfi. 'i'Ihe plate is" connected through high resistance 45w a point of positive potential WithinbatteryIS. In'oneexample the electronswere focused into a' -beam passing to the i "anode when the gridwires were at -35jvolts, plate +200 volts and anode-+224 volts.*For

grid potentials either above or'belowthis value theanode current was decreasedi For grid voltf ages'more positive than this value, an increase in "negative bias on the grid wires increased the anode current andin this region the characteristic of the tube. therefore exhibited negative transconductance (e. g., 160 micromhos)'. On "the negative sideor the focus value of bias the tube exhibited theusual positive transconductanc'e. When the beam is focusedthere is a constant ratio between negative grid-potential and "positive plate potential. I,

Referring'to Fig. 13, the action'of this circuit is as follows: starting'with the grid wires 4|, 42 sufliciently negative to cutofi all electrons, this bias is gradually reduced bymovement of the slider along resistance toward the rightQWhen the cut oif voltage is passed electrons will start to flow, principally to the plate 4 and will set up current flow inthe external resistance 45, thus. lowering the potential of bias is made still less negative and. consequently, the plate voltage is made less positive, the ratio of platevoltage to grid bias is approached corresponding to the conditionof focus. When such conditioriis reached the: electrons will be focused off the plate onto theanode 5 and the decreased -"current in the resistance 45 will give rise to inplate 4. As the grid triggering on action proceeds as previously de scrib'edbyfocusing the electrons off the plate onto the anode with consequent increase in potential of the plate [and greatly augmented space current flow. When th tube thustriggers on the condenser 41 discharges through the tube morerapidly than the charge ca'n bebuilt up through resistor 46. This discharge path through the-tube is almost entirelybetween the anode 5 and the cathode, since the beam is at this time well focused} As the condenser discharges the potential fallslowering the potentials of both plate 4 and anode 5 and weakening the focusing effect until eventually the pote'ntialofthe plate 4 is no longer able to sustain the discharge 'with the existing negative grid potential andthe tube triggers oif. The condenser 41 then begins to charge again through'resistance and the proceSs; repeats itself. The oscillations maybe taken oif to a suitable load circuit from across resist- Fig. lo'showsa cycle of operation in which the triggering action may be accomplished on both sides of focus. For this condition, the plate supply potential was 1'75 volts, the anode potential was 197 voltsand the resistance (Fig-J13) was 2 inegohms. With the grid potential initially at zero a negative bias of 12- volts causes the tube to trigger on after which itmay be triggered off by either a positiVesWing of the gridbias to 4 volts or a still further negative swing of the grid bias to '-.#36.volts. By decreasing numerically the creased potential on the plate 4 drawingiorth more electrons and augmentin the condition of focus. The action is thereforeregenerative andthe electronswill suddenly focus intoa beam (or two beams) on the anode; that is, the tube will atrigg'er on;

1 a After the focused ""infocus due to the action of the plate potential. In other words, the focused condition is stable. If, however, the grid bias is made sufiiciently neg- "ative, the plate can no longer maintain the condition'of focus and thetube will trigger off.

The characteristic curve i corresponding to this cycleof operation is shown in Fig. 14(- This characteristic was obtained with an anode potential 012 24 volts, a plate potential of 200 volts and with avalue of resistance 45 equal to zmegohms. -The tube triggered on at a grid potentialof value Icandtriggered oif at grid potential 7 with increasizig negative grid potential. 1

As in themagnetically focused case the electroe statically focused tube may also betriggered on conditionis established the :grid bias may be increased or decreased over a j considerable range and the tube will hold itself negativebias from greater than .32 volts to less than +32 volts the tube is made to trigger on.

Fig.rl8 represents in diagrainamodified strucltu're in whicha positive grid fiiliis used adjacent the cathode for increasing the space current at low voltages and for protectingthecathode In this case the focusing grid wires 34! and 42 are be hollow cylinders.

made of large diameter andcould advantageously Such a structure has the "advantage of reducingthe anode currentbefore triggeringon and increasing it after the tube has 1 positive from battery 5|.

triggered on, v i 5 Fig. 19 illustrates a. circuit using the typeof tube shown in FigplB, the grid being. made Input variations are supplied from terminals'52 through series coupling condenser 53 .to the focusing grid Wires 4|, 42. The load is taken ciiin any suitable manner such as through outputtransfcrmer 54.

, Fig j20m-illustrates a modified type of electrostatically focused tube in which the plate 4 is andyoff by holding the grid bias constantand "varying" the potential supplied to the plate and anode; the cycle for this operation being shown in F135 154;"Th9tl1be ered on when the anode voltage was slightly increased in the region of the value mhand "triggered off for descending valuesof anode voltage when the voltage 11. was reached. The grid wires were held at -20 volts,

" the plate supplypotential was 200 volts and the space current starts flowing to the plate 4 andthe divided into four quadrants andin which there are two pairs of anodes 5 and fourbeams; the

focusing grid wires are shown at 4|, 42, 4|, 42'. V

' Several illustrativeembodiments of the invention have been given to indicate that the invention is capable of a variety of embodiments and applications. "The forms disclosed are "to be taken illustrative and are not to be construed as limiting the invention the scope of which fined in the claims whichfollow.

1. In combination, a space discharge device is de- What is claimed is:

having a cathode, and output electrodes comprising an anode and a plate, means to apply steady positive voltage to said anode and plate, beamforming means for the emission from said-cathode, said emission, whennot formed into a beam,

V dividing between the anode and plate, means controlled by emission going to the plate for causing the beam-forming means to increase the proportion, of the total emission goingto the anode, means controlled by an"increase in emission to the ano e r ca sin said .beamvfor ins me n t t i ement the increa thenrs i nwe th total; emission going to ,the anode, and extern circuit means responding to the variationin emission going to one of saidfou-tput 3 electrodes. 2. The combination as 1 recited claim" ;1,

' w i h d b amrif r i s me ns o -miscar a netic focusing means-including an electromagnet aving a W ndin andim ans d rivinej urr nt .io

. aid-wi di a r m n'e, oisaidoutpu elm od s- ,BJ'Ifhe combinationas recited i, V which said beam-formingmeans comprises a grid adjacent the cathede, and means for controlling the relative steady-potentials of said-cathode,

grid andplate; L,

4. In combination, a space discharge device having a cathode, an'anode and a plate, means to apply steady positive potential to said anode and plate, means controlled by an applied voltage .for. focusing the emission from said'cathode into a beam, said anode and platebcing p sitioned so that both receive'ein'ission from the cathode when the cathode emission is'not focused into a beam 1 but a greatly increased proportion of the emission goes to the anode when the cathode emission and plate, and means responsive to a decrease in the flow, of plate current in said output circuit for both fccussing the beam on said anode and greatly increasing the strength of the beam; 5.?In combination, aflspace. discharge device having a cathode, a plate and an anode positiened anode. and. m ns a s b 'incr aseoi en it o e em s o beamiao nete eanecl to in- I ,GI'Sfisastill fulfthenthe emission going to the "anode. a

a atri sert ea or s s claim firinclrudl me aer al? ans n rma y biasin t s t di snee them-o f. p int, and m ans e p v r-9 t- .,as to,th gr d tiln r e e m i n o ar 13sternentiened inerease or emission to the iedm s tion ta e discharg d arha ing a cath des p ez a an a ode, an external magnetic coi lios magnetically focusing the cathede emission intoabearninoident upon the anode,- the cathode emission when not focused into the beam beingdiffuseland going to both said plate .andanode; meansto apply steady positive potential to said anode and plate with respect to said cathode, said focusing coil being serially included in; circuit with both said plate and anode, and a high resistance in serieshetween said plate coil. i 1

11. The combination according to claim 10, in-

Excluding a gridfor controlling the emission to said focused into abeam, an external output circuit connected between said cathode and saidaanode plate and anode, means normally biasing the grid negatively beyondcut-pff, and means to apply' input voltage variations to said grid to inito receive emission iromxsaid cathode, a source of steady voltage having its negative terminal connected to saidcathode and a positive terminal connected to each'said'plate and anode, a resist'ive impedance connected between said'plate and l the point-of connection of the plate to said positive terminal, means to focus the cathode emission into a beam incident upon saidanode, means toluse the current flowing through saidresistive impedance to control thexfocussing of said beam and means controlled by anode current to vary "the focusing ofsaidbeam. I

v 6. In combination, 'ia space discharge device. having a cathode/a plate and an anoderhoth positioned to receive emission, from said 'pathode when the "emission-is difiuse, means controliled by emission strikin the plate tor causing the. emission to be focused upon the anode and means re- 'sponsiveto a decrease in emission striking the ,plate, for causing increased electron current to the anode.

7. In combination, a space dischargesxlevice ,havin'ga cathode, a plate and an anod hoth po- -=sitioned to receive emission from said cathode when the emissionis. di fiuse,-mea ris controlled jointly by emission striking the plate and by emission striking the anode for causing the'emission to be focused upon the anode, and means responsive to a decreasei-n emission striking the plate for causing increased --electron current to the anode. j I

. 3. A trigger tube cOmprising alcathode, -a plate and an anode, means to apply positive voltage .to

r the plate and anode, said plate .and anode being both positioned to, receive emission from the leathode, means responsive .to an increase in emission tothe plate .to concentrate thefpmissioninto '.a beam and cause a greater proportion of the total cathode emission to go tosaid anode, means caused-by theconsequent decrease in the portion of the emission going to the ,plate to increase :the intensity of the emission heam going to, the

" said cathode and both said p tiate current flow tosaid plate and anode,

12., lhe combination according to claim 1-0, including asecond resistance connected between said positive potential applying means and said ffocusing coil andfa -oondenser connected irom a point between saidsecpnd resistance rand ooil to said cathode, whereby said combination operates as a relaxation oscillator.

13. An Jim-pulse pnorlucingcircuit. comprising a space discharge device having; an electron emitting cathode, a plate and an anode, anexternal circuit from the cathode to said p eano means to'focus'the eletroneinissioninto a beam going to the anode; said emission when not ro cused going mostly to the plate, means'responsive' to current in saiclexternal circuit for .con-

' trolling the focusing the tr be an enrissionecontrolling eleetrode, a SQuree of control i-mpulses thereier, means to derive positive impulses from a, portion oisaid outpu I circuit connected to said plate, and; means to \derime negative'impulses from a portion of said output circuit connected to said anode: I v p 14. A space, discharge dew-ice an electron emitting cathode, plate an anode, an external circuit connecting said cathode to said plate and anode, means to iccus the electron emission intoaloeamon said anode, said emisden t (mostly-upon the second positive electrode,

and em s i he zret ie i se eeiaa ly he s s t -e e rod m an to stay tocusi-n oltage to the foousingg-rid, a highgresistance between the positi; e y olt-age source }a-nd St .e t elec i a. ei res nses s e connected to :the second-positive eleetrode and means-to trig Qrsaid device on by greduetioniof the focusing voltage toward a 'yalue :atyvhieh the ished.

16. In combination, a space discharge device having a cathode, an anode and a plate both po sitioned to receive emission from said cathode, a resistor connected in series with the plate, a source of positive voltage connected through said resistor to the plate and connected to the anode, means responsive to an increase in emission to the plate to concentrate the emission into a beam and cause a greater proportion of the total cathode emission to go to the anode, resulting in a decrease of emission current to the plate, a corresponding decrease in potential drop across said resistor and a consequent increase in plate potential, said increase in plate potential greatly augmenting the space current by drawing out more electrons from the cathode.

17. In combination, a space discharge device comprising an electron emitting means, a plate and an anode, a source of voltage for applying positive potential to the plate and anode with respect to the cathode, a high resistance connected between the plate and the positive pole of said source, and means for focusing the electron emission from said emitting means into a beam, said emission when not focused mostly striking said plate and when sharply focused striking substantially entirelysaid anode, said focusing means depending for its effectiveness on the plate potential and operating in response to large emission current to the plate with consequent lowered plate voltage to focus the beam off the plate onto the anode, causing the plate potential to rise and accelerate emission to the anode.

ALBERT M. SKELLETT. 

